Typical user communication devices employ a modulated power supply system that includes radio frequency (RF) switching converters to generate one or more supply voltages to power RF circuitry. If an RF switching converter provides envelope tracking (ET) and/or average power tracking (APT), a supply voltage level of the supply voltage may need to be controlled with adequate precision in order to provide adequate power performance and to prevent unwanted distortion. In an ET system, there is a need to have a modulated power supply system that is configured to operate in ET mode and in APT mode. When the modulated power supply system is operating in APT mode at or near 100% duty cycle in buck mode, no regulation against battery voltage changes is available. If the battery voltage drops quickly during APT mode, a typical transceiver control system communicatively coupled to the modulated power supply system will not have time to react to configure the associated RF switching converter into a 1.5×boost mode. As a result, there is a need for a modulated power supply system and method having an automatic transition from a buck mode to a boost mode and vice versa to minimize undesirable effects due to battery voltage fluctuations.